parathyroid gland Flashcards
eclampsia
puerperal tetany
milk fever
life-threatening drop in blood levels of calcium that strikes some nursing dogs, cats and cows
hypocalcemia tetany is due to
Increase in excitability of nerve and muscle cells due decrease calcium
spastic skeletal muscle contraction
calcium decrease causes what channels to be unblocked?
NA channels
NA increases and depolarization threshold is more atteinable causing activation of neurons
neurons are unstable and fire spontaneous action potentials that trigger the involuntary contraction of muscle leading to tetany
what hormone does the parathyroid gland secretes?
parathyroid hormone (PTH)
major hormone to raise blood calcium level
parathyroid hormone (PTH)
calcium is needed for
blood coagulation
secretion
cell function
neural transmission
muscle contraction
Three hormones regulate blood calcium level
parathyroid hormone (PTH)
active vitamin D3
calcitonin
PTH is produced and secreted by what cells is the parathyroid gland?
chief cells
in chief cells PTH is first synthesized as
Pre-proPTH
chief cells become active in response to
decreased calcium levels
mechanism of activation of chief cels
chief cells detect low blood calcium levels and in response increase secretion of PTH
t/f PTH raises blood Ca2+ levels without promoting the deposition of calcium phosphate crystals in bone
true
PTH is increased by two causes
decreased Calcium or increased calcium phosphate crystals in BLOOD
3 mechanism of action of PTH
- stimulates activity of osteoclasts to promote reabsorption to release calcium
- stimulates kidneys to reabsorb calcium from renal filtrate while inhibiting the reabsorption of PO43
- stimulates kidney to convert D3 to it’s active form raising blood calcium levels indirectly
promoting : Ca2+ and PO43- absorption in small intestine and reabsorption in kidney
synthesis of active vitamin D3 =1,25(OH)2D3= calcitriol
- vitamin D3 is produced in the skin under influence of sunlight
- converted to active form in liver and kidney
PTH stimulates the activity of what enzyme in the kidneys to help converting vit. D3 to calcitriol?
hydroxylation enzyme
what promotes calcitriol?
Ca2+ and PO43- absorption in small intestine and reabsorption in kidney
t/f The effect of simultaneously raising the blood concentrations of Ca2+ and PO43- results in the increased tendency of these two ions to precipitated as hydroxyapatite crystals in bone
true
mechanism of PTH activation of osteoclast for reabsorption and release of calcium
- PTH has receptors on osteoblasts, but NOT in osteoclasts.
- PTH stimulate osteoblasts to produce RANKL (Receptor-Activator of Nuclear Factor κB Ligand).
- Binding of RANKL to RANK on preosteoclast promote its differentiation into mature osteoclast, thereby causes bone resorption.
t/f PTH has receptors on osteoblasts, but NOT in osteoclasts.
true
PTHrP parathyroid hormone related protein functions
acts on PTH receptor to mimic the role PTH
increases bone resorption, stimulating the renal reabsorption of Ca2+
promotes renal excretion of PO43+ causes hypercalcemia
t/f PTHrP is also secreted by many types of cancers
true
t/f PTHrP causes hypocalcemia
false
cause HYPERCALCEMIA
in Malignancy-Related Hypercalcemia (Pseudo-hyperparathyroidism) how are the levels of PTH and PTHrP?
PTH normal or low
PTHrP high
2 types of hyperparathyroidism
primary and secondary
occurs within parathyroid glands
in Parathyroid tumor or cancer
Hypercalcemia =elevated level of blood Ca2+
causes kidney stones
Primary hyperparathyroidism
occurs outside parathyroid glands, through hypocalcemic Ca2+ negative feedback
in Rickets /Osteomalacia
Vitamin D3 deficiency
Chronic renal or celiac disease
Lack of dietary calcium
Hypocalcemia =decreased level of blood Ca2+)
secondary hyperparathyroidism
Lack of dietary calcium can cause
secondary hyperparathyroidism
weakening of the bones due to excessive resorption of bones
osteoporosis
In hypothyroidism how are the levels of PTH?
LOW = low levels of calcium
What can cause hypoparathyroidism?
Accidental injury to or removal of parathyroid glands in thyroidectomy surgery
Cancer radiation treatments
Autoimmune reactions
In pseudo-hypoparathyroidism, how are going to be the levels of PTH?
normal or high
clinical signs of hypoparathyroidism
Muscle aches or cramps
Muscle spasms, especially around the mouth
Tingling, burning, or numbness in the fingertips, toes, and lips.
Seizures
Osteoporosis
calcitonis is produced by ________in response to _________
parafollicular cells
increased blood calcium
calcitonin is the contraregulatory hormone of
PTH
Inhibits osteoclastic activity = inhibits bone resorption
Inhibits Ca2+ absorption in the intestines
Inhibits of Ca2+ reabsorption in the kidneys
calcitonin
what is the hypothesis for the use of calcitonin?
useful during Calcium stress protecting bone
growth
pregnancy
inihibiting postpandrial hypercalcimia
inhibits postpandrial hypercalcimia
calcitonin
t/f salmon can be used to treat hypercalcimia
true
disease induced by excessive bone remodeling, caused by osteoclastic activity
Paget’s disease
decrease in extracellular Ca2+ concentrations or an increase in phosphate (PO43-) concentrations leads to
PTH secretion from the parathyroid glands
increases renal reabsorption of Ca2+
renal activation of vitamin D3 urinary PO43- excretion
bone resorption
PTH
increases intestinal absorption and renal reabsorption of Ca2+ and PO43-
active vitamin D3
An increase in Ca2+ concentration stimulates the thyroid gland to secrete _____ to inhibit ____
calcitonin to inhibit osteoclastic bone resorption
